DescriptionX-ray diffraction is a useful method for studying the absolute structure of a molecule or complex in crystalline form. Analysis and determination by this technique provides information on atomic positions within the molecule as well as bond lengths, angles, unit cell, space group and symmetry. We used X-ray analysis to study hydrogen-bonding interactions in a number of molecules. A hydrogen bond occurs between a hydrogen atom covalently bonded to a first row electronegative atom and weakly bonded to another first-row electronegative atom having at least one lone pair of electrons. Hydrogen-bonding interactions affect the coordination and complexation of molecular compounds. In this paper, we examine a structural anomaly of a far-too-short hydrogen bond in H5O2+cation and describe the various methods employed to resolve this issue. We also investigate intra- and inter-molecular hydrogen bonding in an oligosaccharide, as well as sulfate ion coordination due to hydrogen bonding in two different macrocycles.